Touch panels, each combining an input device and a display device (display), are installed on computers, mobile information terminals, and other electronic information equipment.
Touch panels are available in various types, such as the capacitance type, resistance membrane type, ultrasonic surface elastic wave type, and optical type (infrared optical imaging type).
For example, the capacitance type (refer to Patent Literature 1) adopts a mechanism where electrodes are placed in a matrix pattern inside the panel, and when the user touches the panel with his/her finger, etc., the resulting change in capacitance is used to detect the coordinates.
Also, the resistance membrane type (refer to Patent Literature 2) adopts a mechanism where two membranes are placed in a manner facing each other and constantly receiving voltage from their both edges, and when the user touches the panel, the membranes contact each other and the resulting change in the voltage at this position is used to detect the coordinates.
Further, the optical type (refer to Patent Literature 3) adopts a mechanism where infrared LEDs and image sensors (cameras) are placed at the left and right corners of the top side of the panel, while retroreflective tapes that reflect the incident light in the incident direction are placed on the left side, right side, and bottom side of the panel. When the user touches the panel with his/her finger, etc., and thereby blocks the infrared light, the resulting shadow is captured by the image sensors and the coordinates are detected by triangulation.